Comparison of the Available American Elm Cultivars

(Compiled by Bruce Carley, February 13, 2007)

    DED-tolerance level: Higher than any other American elm yet known; seemingly comparable to the best Asian elm cultivars and hybrids. (See USDA report from 1995; Read about one tree's survival.
    Growth rate: Rapid when conditions are favorable.
    Early growth pattern: Flimsy, arching, and top-heavy when left to its own devices; requires frequent attention to training and pruning in its first few years to develop a straight, central trunk up to at least 10-20 feet above the ground, and to guard against potential splitting at weak crotches. (See pruning guidelines.)
    Mature form and size: Seems to develop the classic, vase-like American elm shape, once established, and without any structural problems. The largest known example is still relatively young, so its eventual height can only be inferred at this time, but its developing form and rate of growth suggest that it may reach higher than most other American elm cultivars. (See photograph.)
    Other notes: Reliably hardy in northern climates, probably well into zone 4. The necessary early training can be accomplished easily enough by those who are committed; detailed guidelines on training and pruning are always available at

    DED-tolerance level: Adequate for planting; may not be better than fair. (See USDA report from 2005.)
    Growth rate: Generally slow at first, moderate to rapid when well established.
    Early growth pattern: Vertical with uncommonly narrow branching; minimal need for training.
    Mature form and size: V-shaped with numerous central limbs, but not vase-shaped; moderate height. (See photograph.)
    Other notes: Winter hardiness in northern latitudes seems inconsistent if not questionable; winterkill has been observed more than occasionally in east-central Massachusetts.

    DED-tolerance level: Fairly high, with a high (though not perfect) rate of survival in field plantings over many decades. (See USDA report from 2001.)
    Growth rate: Rapid when conditions are favorable.
    Early growth pattern: Broadly vertical, soon forming a wide, maple-like oval shape; minimal need for training. (See photograph.)
    Mature form and size: Moderate height, with many angular side branches, much like an oak; generally lacking the classic vase shape of the species. (See photograph.)
    Other notes: Selected in the 1920's for its early growth form and resistance to elm yellows; very suitable for urban use and especially for those who prefer not to invest much time in early training and pruning.

    DED-tolerance level: Seemingly fairly high, based on minimal information. (See USDA report from 2005.)
    Growth rate: Moderately rapid once established.
    Early growth pattern: Vertical, with minimal need for training.
    Mature form and size: Spreading and shapely, with curved branching; very moderate in height. (See photograph.)
    Other notes: Seed germination rate is extraordinarily low, suggesting an inbreed; until recently, this cultivar was widely thought to be a triploid hybrid.

    DED-tolerance level: Low in most clones; may be fair at best in others. (See footnote; Read about field observations.)
    Growth rate: Rapid in all six clones when conditions are favorable.
    Early growth pattern: Strongly arching in clone W-507, requiring intensive staking; remaining clones vertical with minimal need for training. (See photograph.)
    Mature form and size: Seemingly more or less typical of the species in all six clones.
    Other notes: Unanswered questions abound in connection with this six-clone series; clone identities are usually masked and difficult to determine.

Main article: Saving the American Elm